An Ultra-Thin Crosslinked Carbonate Ester Electrolyte for 24 V Bipolar Lithium-Metal Batteries

Fabrication of an ultrathin solid electrolyte with high conductance is essential to achieve high energy density of solid-state batteries. As solid polymer electrolytes (SPEs) are characterized by good ductility, ease of manufacturing, and low cost, the current solvent-based casting pathway suffers from the difficulty in controlling the thickness. In addition, the low ionic conductivity and narrow electrochemical window of the polyether-type SPEs further hinder their practical applications. We fabricate an ultra-thin solid-polymer electrolyte by in situ polymerization of carbonate ester vinyl ethylene carbonate and poly(ethylene glycol) diacrylate using a porous polypropylene membrane as a support. The obtained solid electrolyte is of only 8 mu m and possesses an unprecedented ionic conductance of 83.3 mS at room temperature. Furthermore, the electrolyte is compatible with Li metal and can suppress dendrite growth. An all-solid-state lithium battery based on LiFePO4 cathode can operate stably for over 150 cycles with 86% capacity retention. The non-fluidic nature of the electrolyte further enables the fabrication of an energy-dense 24 V bipolar pouch cell which demonstrates extreme flexibility and safety. No voltage drop is observed upon folding and cutting. This in situ polymerized ultra-thin electrolyte provides a promising platform for the fabrication of high-energy solid-state batteries and also a potential candidate for flexible batteries.